1. Field of the Invention
The present invention relates to a power supply terminal having a noise filter part and a back wiring board (BWB) assembly using the power supply terminal.
2. Description of the Related Art
With recent progress and development of various communication systems, such as cellular telephones and the Internet, in various forms, the amount of information handled by the various communication systems has been continuing to increase in various forms. There is a tendency to require of the various communication systems higher information density, higher transmission capacity, and higher-level functions. In order to satisfy these requirements, communication apparatus forming the various communication systems tend to consume more power. Hence, the communication apparatus need to be configured so as to withstand a large current. At the same time, to process high-density and high-frequency signals, the number of layers in the structure of a back wiring board (BWB) included in each communication apparatus is increasing steadily and also the BWB tends to be increasingly thickened.
Typically a power supply terminal is connected to the BWB of such a communication apparatus by using a press fit terminal without soldering. A typical conventional power supply terminal includes a crimp contact for supplying power, a press fit terminal inserted into the BWB, and a terminal member (terminal block) where part of the press fit terminal is housed. The crimp contact is electrically connected to the press fit terminal by a screw. The power supply terminal is inserted into the BWB from one side of the BWB. A plurality of capacitors for forming a noise filter circuit are mounted on an underside of the BWB with respect to a direction of the insertion of the power supply terminal. The noise filter circuit is provided for measures against EMI. For example, noise caused to a power supply line might adversely affect another apparatus connected to the same power supply line.
IEC international standards are set to deal with this problem. Although the IEC standards are used as they are in Europe, various countries adopt their own standards; for example, Japan adopts VCCI standards and the U.S. adopts FCC standards. In the method of connecting the conventional power supply terminal as described above, the capacitors included in the noise filter circuit are mounted directly on the BWB. Therefore, if this BWB warps when the press fit terminal is inserted into or pulled out of the BWB, when an electronic circuit package is inserted into or pulled out of a connector mounted on the BWB, or when the BWB is fitted on an enclosure for the apparatus, a capacitor included in this noise filter circuit will be damaged.
Furthermore, parts such as connectors or the like which cannot withstand reflow soldering are mounted on the BWB. In consideration of efficiency in work performed to mount parts on the BWB, the capacitors included in the noise filter circuit are mounted on the BWB by manual soldering with a soldering iron. Therefore, a capacitor included in this noise filter circuit may be damaged also by thermal stress at the time of this soldering.
A power supply terminal that overcomes these problems is disclosed in International Publication No. WO01/99237 of an application by the present applicant. In the power supply terminal described in the international publication, capacitors are mounted on a noise filter circuit board separate from a BWB by reflow soldering, and the noise filter circuit board is soldered to press fit terminals and housed in a terminal member.
However, the above power supply terminal described in the international publication is poor in manufacturability because the noise filter circuit board is attached to the press fit terminals by soldering. In addition, the power supply terminal is of a large size because the terminal member needs to be provided with a region for housing the noise filter circuit board.